reproduce (this is a W=1 build):
        # https://github.com/Rust-for-Linux/linux/commit/db702816ad4d1d0ae54a5443c8865448f2dde75f
        git remote add rust https://github.com/Rust-for-Linux/linux
        git fetch --no-tags rust rust-next
        git checkout db702816ad4d1d0ae54a5443c8865448f2dde75f

        # install um cross compiling tool for clang build
        # apt-get install binutils-um-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um prepare